In optical devices such as a Faraday rotator, a polarizer, a wavelength conversion element, a laser crystal, a lens, a wavelength plate, a beam splitter, an electro-optic element, and an acousto-optic device, a crystal body configured with a crystal is used. Such a crystal body generally has a pair of light passing surfaces which face each other and pass light and at least one side surface which connects the pair of the light passing surfaces.
For example, Patent Document 1 listed below discloses that such a crystal body is used as a Faraday rotator.